1. Field of Invention
The present invention relates to a cathode ray tube and a funnel therefore. More particularly, the present invention relates to a cathode ray tube and a funnel included in the cathode ray tube, in which an installation position of an anode button to which a high voltage is applied is optimized in order to respond to slimming trend in which length overall becomes shorter.
2. Description of the Related Art
Generally, a cathode ray tube (CRT) is a display device for realizing a certain image by emitting electron beams corresponding to electric signals so as to hit a phosphor screen, thereby converting the electron beams to an optical image.
FIG. 1 is a sectional view illustrating the structure of a cathode ray tube according to a related art.
As shown in FIG. 1, the related art cathode ray tube includes a panel 2, a screen 4 installed inside the panel 2 and coated with a phosphor, a funnel 6 coupled to a rear surface of the panel 2, an electro gun 8 connected to a rear portion of the funnel 4 for emitting electron beams toward the phosphor on the screen 4, a deflection yoke 10 for deflecting the electron beams emitted from the electron gun 8, and a shadow mask 12 mounted on a rear side of the panel 2 for selecting a color of the deflected electron beam.
The operation of the above described cathode ray tube is described in detail with reference to FIG. 1.
Electron beam is accelerated and converged while passing through each electrode of the electron gun 8, and the accelerated and converged electron beam is deflected by the deflection yoke 10 installed in the panel 6 while moving toward the panel 6.
The deflected electron beam passes through a slot of the shadow mask 12 and hits the phosphor on the phosphor screen 4. At this time, the phosphor on the phosphor screen 4 is excited due to energy of the electron beam and irradiates visible light rays, thereby forming an image on the phosphor screen 4.
FIG. 2 is a sectional view illustrating some important portion of the cathode ray tube according to a related art.
As shown in FIG. 2, an anode button 20 for transferring a high voltage, for example about 30 Kv, to the electron gun is installed to the funnel 6 so that the electron beam emitted from the electron gun is accelerated and converged toward the screen, and an insulator 22 is installed to an exterior of the funnel 6 in such a manner of surrounding the anode button 20.
A value A is a distance on the central axis of the funnel between a seal edge (SE) face of the funnel 6, which abuts the panel 2, and the center of the anode button 20. On the other hand, A value B is a distance on the central axis of the funnel between a neck seal (NS) of the funnel 6, disposed at the opposite side of the seal edge of the funnel 6, and the center of the anode button 20. A value T is a B to A ratio (B/A), and the anode button is disposed to meet the condition of 2≦T<2.8.
The insulator 22 is generally formed of a nonconductive material, such as silicon, and its minimum size is limited in the range of capable of insulating the anode button 20.
Recently, as the cathode ray tubes are getting larger and slimmer due to severe competitiveness, technologies for reducing length overall of the cathode ray tubes are being developed. Still, in the case in which the anode button 20 is designed to be disposed at a position which meets the condition 2≦T<2.8, there is a problem in that the anode button 20 and the insulator 22 can mechanically interfere with the deflection yoke 10 since the anode button 20 and the deflection yoke 10 are positioned so close to each other. That is, sizes of the anode button 20, the insulator 22 and the deflection yoke 10 are limited or it is difficult to install the anode button 20, the insulator 22 and the deflection yoke 10 due to the small installation space.
Further, since the anode button 20 and the deflection yoke 10 are positioned so close to each other, a high voltage applied to the anode button 20 affects deflection magnetic field generated from the deflection yoke 10, resulting in distortion of the deflection magnetic field. This results in screen distortion as shown in FIG. 3.